This program will produce the HIV envelope proteins and the T4 glycoprotein from a variety of expression vectors designed to make the proteins in bacteria, yeast or mammalian cells. The program will function as a core to provide material to virtually all of the other programs. It will supply native gp120/gp41 and native T4 as well as mutated forms and fragments of these proteins to the other groups. A goal of this program is to develop even better systems to express gp120/gp41 and T4 then the ones presently available. This will include the development of SV40 packaging vectors and the creation of cell lines expressing high levels of the proteins of interest. The program will also study the regulation of HIV envelope gene expression and examine the effect of the transactivating factors TAT and ART on expression from various vectors.